In recent years there has been a huge increase in the demand for cost-effective communications networks. One of such networks is a telephone wire network that uses telephone line wiring existing in a building, such as Plain Old Telephone Service (POTS) line wiring, as a medium for the data transmission between computers.
In telephone wire networks, the arrival position in time of a received band limited pulse may be used to convey digital information. The waveform of a received band limited pulse is illustrated in FIG. 1. Conventionally, the arrival position of a received pulse is detected using a waveform envelope representing the absolute value of the received signal (FIG. 2). The envelope is supplied to a slicing circuit having a threshold level selected to identify the arrival position of the received pulse. When the envelope crosses the threshold level, the slicing circuit detects the arrival position of the pulse.
However, in telephone wire networks, a received envelope waveform depends largely on the wiring topology. As the wiring topology may cause multiple signal reflections, the shape of a received pulse may be so distorted that the envelope will have multiple localized maximum points. In addition, the wiring topology varies from place to place. Therefore, the distortion of the received pulse is unpredictable.
FIG. 3 illustrates the waveform of a received pulse signal having multiple localized maximum points due to wiring topology. FIG. 4 illustrates the waveform envelope of such a pulse signal. In response to the waveform envelope having multiple maximum points, a slicing circuit may identify multiple pulse positions, at which the envelope crosses a threshold level. As a result, a unique time value for the arrival position of a received pulse cannot be detected. This can cause data recovery errors.
Thus, it would be desirable to provide a pulse position detector capable of identifying a unique pulse arrival position even if the received pulse is highly distorted.